TWI585111B - Plastic wrap - Google Patents

Description

plastic wrap

The present invention relates to a wrap film, and more particularly to a wrap film containing a polyvinylidene chloride-based resin.

It is known that a film composed of a polyvinylidene chloride-based resin (hereinafter, abbreviated as "PVDC resin") has excellent properties such as adhesion, transparency, barrier property, heat resistance, and flavor retention, and is suitable for use as a film. A film for a household wrap film (for example, Japanese Laid-Open Patent Publication No. 2011-168750 (Patent Document 1)). Such a PVDC resin wrap film is wound around a core material, and is placed in a dedicated carton as a wrap film wrap. Then, when you want to use it, take out the plastic wrap of the required length from the paper tray and cut it with the serrations installed on the carton.

[First technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2011-168750

However, when the PVDC resin wrap film is taken out from the paper cassette and cut with the serrations mounted on the paper cassette, there may be a case where the wrap film is torn in the longitudinal direction or the serration is aged. Therefore, the inventors waited for such defects The reason for the situation was found to be because the force applied when cutting the wrap film was large.

The present invention has been developed in view of the above problems in the prior art, and it is an object of the invention to provide a PVDC resin wrap film which can be easily cut with a small force.

In order to achieve the above object, the inventors of the present invention have conducted intensive studies and found that the PVDC resin wrap film having a birefringence difference and a planar orientation degree satisfying predetermined conditions can be cut with a small force, thereby completing the present invention.

That is, the wrap film of the present invention contains a wrap film of a polyvinylidene chloride-based resin, which is represented by the following formula (1): Δn = n _{x -} n _y = Re / d (1) (wherein n _x represents the refractive index in the slow axis direction of the film, n _y represents the refractive index in the direction perpendicular to the slow axis direction of the film, Re represents the in-plane hysteresis of the film (unit: nm), and d represents the film thickness ( Unit: nm))

The calculated birefringence difference Δn satisfies the following formula (1a): The condition expressed by the following formula (2): ΔP = (n _x + n _y ) / 2 - n _z (2) (wherein n _x represents the refractive index in the slow axis direction of the film, n _y represents the refractive index in the direction perpendicular to the slow axis direction of the film, and n _z represents the refractive index in the thickness direction of the film)

The calculated plane orientation degree ΔP satisfies the following formula (2a): The conditions indicated.

The thickness of the wrap film of the present invention is preferably 5 to 15 μm. Further, as the polyvinylidene chloride-based resin, a copolymer of vinylidene chloride and a comonomer copolymerizable with the vinylidene chloride is preferable, and as the comonomer, vinyl chloride is preferable. Further, it is preferable that the slow axis direction in the plane of the film is the longitudinal direction (MD) of the wrap film. In addition, the machine direction (MD) refers to the direction of movement of the film when the inflation is biaxially extended.

The longitudinal direction (MD) of the wrap film of the present invention is a winding direction, and is used in a state of being wrapped in a wrap film wound body in a zigzag-mounted carton.

According to the present invention, it is possible to obtain a PVDC resin wrap film which can be easily cut with a small force.

1‧‧‧Exporting machine

2‧‧‧cooling bath

3‧‧‧Warm bath

4~6‧‧‧roller

7‧‧‧Winding roller

Fig. 1 is a schematic view showing a wrap film manufacturing apparatus used in Examples and Comparative Examples.

Fig. 2 is a graph showing the results of plotting the birefringence difference Δn with respect to the plane orientation degree ΔP for the wrap film obtained in the examples and the comparative examples.

Hereinafter, the present invention will be described in detail based on preferred embodiments of the present invention.

The wrap film of the present invention will be described first. The invention The wrap film is a wrap film containing a polyvinylidene chloride-based resin (PVDC resin). The PVDC resin used in the present invention is a copolymer of vinylidene chloride (VD) and a comonomer copolymerizable with vinylidene chloride. The content of the vinylidene chloride in the PVDC resin is preferably 60 to 98% by mass, more preferably 65 to 97% by mass, still more preferably 70 to 95% by mass, particularly preferably 75 to 90% by mass; The content of the comonomer is preferably from 2 to 40% by mass, more preferably from 3 to 35% by mass, still more preferably from 5 to 30% by mass, particularly preferably from 10 to 25% by mass. If the content of the comonomer is less than the lower limit, there is a tendency that the plasticization in the PVDC resin is insufficient and the melt processability is lowered. On the other hand, if the upper limit is exceeded, gas barrier properties and water vapor barrier are present. Sex will reduce the trend.

Examples of the comonomer include vinyl chloride (VC); alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, and octadecyl acrylate. The number of carbon atoms is 1 to 18); methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, methacrylic acid An alkyl methacrylate such as an ester (having an alkyl group having 1 to 18 carbon atoms); a vinyl cyanide such as acrylonitrile or methacrylonitrile; an aromatic vinyl such as styrene; or an aliphatic carboxylic acid such as vinyl acetate (carbon atom) a vinyl ester of 1 to 18); an alkyl vinyl ether (having an alkyl group having 1 to 18 carbon atoms); acrylic acid, methacrylic acid, maleic acid, fumaric acid, methylene An ethylene polymerizable unsaturated carboxylic acid such as succinic acid; an alkyl ester of an ethylene polymerizable unsaturated dicarboxylic acid such as maleic acid, fumaric acid or methylene succinic acid (including a partial ester. Carbon An atomic number of 1 to 18); an epoxy group-containing ethylene polymerizable monomer such as glycidyl acrylate or glycidyl methacrylate; a diene monomer such as butadiene or isoprene; and chloroprene A chlorinated diene monomer; a polyfunctional monomer having two or more polymerizable double bonds in a molecule such as divinylbenzene, ethylene glycol diacrylate or ethylene glycol methacrylate; These comonomers may be used alone or in combination of two or more. Among such comonomers, vinyl chloride (VC), methyl acrylate, ethyl acrylate, butyl acrylate, and lauryl acrylate are preferable, and vinyl chloride (VC) is more preferable.

The specific viscosity (η) (unit: L/g) of the PVDC resin is preferably from 0.030 to 0.070, more preferably from 0.033 to 0.065, in view of melt processability, elongation processability, packaging machine suitability, and cold resistance. It is particularly preferably from 0.035 to 0.060 L/g. When the specific viscosity of the PVDC resin is less than the lower limit, there is a tendency that the elongational workability is lowered, or the film strength and the cutting property are lowered. On the other hand, if the upper limit is exceeded, the melt processability is lowered or colored. The trend. Further, in the PVDC resin used in the present invention, two or more types of PVDC resins having different specific viscosity may be mixed, and the specific viscosity may be adjusted to the above range.

Such a PVDC resin can be synthesized by a well-known method such as suspension polymerization, emulsion polymerization, or solution polymerization, but a powder resin having an average particle diameter of 40 to 600 μm can be obtained without performing a pulverization treatment, and is preferably suspension polymerization.

Further, in the present invention, the PVDC resin may be used alone, or a plasticizer, a heat stabilizer, an antioxidant, a lubricant, a dispersing aid, a filler, an ultraviolet absorber, or an interface may be added to the PVDC resin. Various additives such as an active agent and a pH adjuster are used as the PVDC resin composition. The additive may be added to the polymerization reaction system at least at any time before, during, or after the synthesis of the PVDC resin, thereby preparing a PVDC resin composition containing the additive.

Examples of the plasticizer include dioctyl phthalate, tributyl citrate, dibutyl sebacate, dioctyl sebacate, acetylated monoglyceride, and acetylated diacid. A glyceride, an acetylated triglyceride, a polycondensate of adipic acid and 1,3-butylene glycol, a polycondensate of adipic acid and 1,4-butanediol, and the like. These plasticizers may be used alone or in combination of two or more. The amount of the plasticizer added is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, particularly preferably 0.5 to 3 parts by mass, per 100 parts by mass of the PVDC resin.

Examples of the heat stabilizer include epoxy resin oils such as epoxy soybean oil and epoxy linseed oil, epoxy fatty acid esters such as epoxy animal oil and octyl epoxy stearate, and epoxy resins such as bisphenol A glycidyl ether. An epoxy compound such as a polymer; an epoxy group-containing resin such as a glycidyl group-containing acrylic resin or a glycidyl group-containing methacrylic resin. These heat stabilizers may be used alone or in combination of two or more. The amount of the heat stabilizer added is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 4 parts by mass, particularly preferably 1 to 3 parts by mass, per 100 parts by mass of the PVDC resin.

Examples of the antioxidant, the lubricant, the dispersing aid, the filler, the ultraviolet absorber, the surfactant, and the pH adjuster are as described in JP-A-2011-94035.

Further, in the present invention, the PVDC resin may also be used. Mix other resins. The amount of the other resin to be mixed is preferably 30 parts by mass or less based on 100 parts by mass of the PVDC resin, and more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass in view of compatibility with the PVDC resin. the following. In addition, the content of the vinylidene chloride component in the mixed resin of the PVDC resin and the other resin is preferably 50% by mass or more, and more preferably 60% in consideration of gas barrier properties, water vapor barrier properties, and heat resistance. Above the mass percentage, it is particularly preferably 70 mass% or more.

Examples of the other resin include an ethylene-vinyl acetate copolymer, an ethylene-vinyl chloride copolymer, an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, and an ethylene-acrylate copolymer (preferably ethylene-acrylic acid). a base copolymer (having an alkyl group having 1 to 18 carbon atoms), an ethylene-methacrylate copolymer (preferably an ethylene-alkyl methacrylate copolymer (the alkyl group has 1 to 18 carbon atoms) )), a homopolymer of an ethylene-glycidyl acrylate copolymer, an ethylene-glycidyl methacrylate copolymer, an acrylate (preferably an alkyl acrylate (alkyl group having 1 to 18 carbon atoms)) Homopolymers and copolymers of copolymers (for example, methyl acrylate-butyl acrylate copolymer), methacrylates (preferably alkyl methacrylates (having an alkyl group having 1 to 18 carbon atoms)) For example, methyl methacrylate-butyl methacrylate copolymer, ethylene ionomer, methyl methacrylate-butadiene-styrene copolymer, polyamine, and the like. These other resins may be used alone or in combination of two or more.

For example, the PVDC resin or the PVDC resin composition may be melt-extruded by an extruder, formed into a film shape, extended after cooling (preferably biaxial stretching), and then subjected to a relaxation treatment, thereby producing the wrap film of the present invention. It is especially preferred to manufacture the wrap film of the present invention by an inflation biaxial stretching method of a circular mold. At this time, the cooling temperature, the stretching temperature, the stretching ratio, the relaxation temperature, and the relaxation rate of the melt-extruded film are adjusted to ensure that the obtained birefringence difference Δn of the wrap film satisfies the following formula (1a): The condition indicated, the plane orientation degree ΔP satisfies the following formula (2a): The conditions indicated. When the birefringence difference Δn is less than 0.0003 or the plane orientation degree ΔP is lower than -0.0120, the gas-filled biaxially stretched easily breaks, and it is difficult to stably produce a film. Further, if the birefringence difference Δn exceeds 0.0013 or the plane orientation degree ΔP exceeds -0.0102, the wrap film is easily stretched, and it is difficult to easily cut the wrap film with a small force. In view of this, it is preferable that the birefringence difference Δn satisfies the following formula (1b): The condition indicated, and the degree of planar orientation ΔP satisfies the following formula (2b): The conditions indicated.

Further, the birefringence difference Δn is represented by the following formula (1): Δn = n _{x -} n _y = Re / d (1) (wherein n _x represents a refractive index in the slow axis direction of the film in the plane , n _y represents the refractive index in the direction perpendicular to the slow axis direction of the film, Re represents the in-plane hysteresis amount of the film (unit: nm), and d represents the film thickness (unit: nm))

It is calculated that the plane orientation degree ΔP is represented by the following formula (2): ΔP = (n _x + n _y )/2 - n _z (2) (wherein n _x represents the slow axis direction of the film in the plane The refractive index, n _y represents the refractive index in the direction perpendicular to the slow axis direction of the film, and n _z represents the refractive index in the thickness direction of the film).

As the stretching ratio (degree of molecular orientation) of the machine direction (MD) becomes larger, or as the relaxation rate of the machine direction (MD) becomes smaller, the birefringence difference Δn tends to become smaller; in addition, with the stretching ratio When the relaxation rate is small, the degree of planar orientation ΔP tends to be small, so that the stretching ratio and the relaxation ratio can be controlled based on the trends, whereby the birefringence difference Δn and the plane are obtained. The degree of orientation ΔP is adjusted to the above range.

The cooling temperature of the film after melt extrusion may not be determined, and is preferably, for example, 20 ° C or lower, more preferably 15 ° C or lower. When the cooling temperature exceeds the upper limit, the resin is crystallized, and the elongation is deteriorated. In addition, the wrap film is whitened and the transparency is impaired. Further, the lower limit of the cooling temperature is not particularly limited, but in consideration of economy (specifically, cooling ability), it is preferably 3° C. or higher, and more preferably 5° C. or higher.

The extension temperature cannot be determined in any way, and is preferably, for example, 15 ° C or higher, and more preferably 20 ° C or higher. If the extension temperature is lower than the lower limit, there is a tendency that the elongation is deteriorated and the gas-filled bubbles are easily broken. In addition, the upper limit of the stretching temperature is not particularly limited, but in view of workability and economy (large equipment), it is preferably 50 ° C or lower, more preferably 45 ° C or lower.

Regarding the stretching ratio, it is not possible to make a decision, for example, as a stretching ratio in the machine direction (MD), preferably 3.6 to 5.0 times, more preferably 3.8. Up to 4.6 times. If the stretching ratio of the machine direction (MD) is lower than the lower limit, there is a tendency that the gas bubbles are slack, and it is difficult to continuously manufacture the film; on the other hand, if the upper limit is exceeded, there is air backflow, and the shape of the bubble is unstable, resulting in The trend of uneven width and uneven thickness. Further, as the stretching ratio in the transverse direction (TD), it is preferably 4.0 to 5.5 times, more preferably 4.5 to 5.1 times. If the stretching ratio of the transverse direction (TD) is lower than the lower limit, there is a tendency that the shape of the bubble is unstable, resulting in uneven width and uneven thickness. On the other hand, if the upper limit is exceeded, the bubble tends to be broken.

Regarding the relaxation temperature, it is not possible to make a decision, preferably, for example, 20 to 100 ° C, more preferably 25 to 85 ° C. If the relaxation temperature is lower than the lower limit, there is a tendency that a sufficient relaxation rate cannot be obtained, and the winding is too tight, and the core portion is deformed. On the other hand, if the upper limit is exceeded, the transparency of the film is present. The trend of damage.

Regarding the relaxation rate, it is not possible to make a decision, for example, as a relaxation ratio in the machine direction (MD), it is preferably 4.5 to 12.0%, and more preferably 5.0 to 11.0%. If the relaxation rate in the machine direction (MD) is less than the lower limit, there is insufficient relaxation, and when the wrap film wrap is produced, there is a tendency that the wrap around is too tight; on the other hand, if the upper limit is exceeded, there is The film is slack and tends to wrinkle when wound up. Further, as the relaxation ratio in the transverse direction (TD), it is preferably from 2.5 to 6.5%, more preferably from 3.0 to 6.1%. When the relaxation ratio of the transverse direction (TD) is less than the lower limit, there is a tendency that the width of the film changes after the wrap film is formed. On the other hand, if the upper limit is exceeded, wrinkles are likely to occur during winding. trend.

The thickness of the wrap film obtained in the above manner is preferably 5 to 15 μm. If the thickness of the wrap film is lower than the lower limit, there is no The method obtains sufficient strength and tends to be broken when used; on the other hand, if the upper limit is exceeded, there is a tendency that a large force is required for cutting, and there is a tendency that the rigidity is increased, and the adhesiveness is deteriorated in practice. .

Further, in the wrap film of the present invention, it is preferred that the slow axis direction in the plane of the film is the longitudinal direction (MD) of the wrap film. Further, the wrap film of the present invention is preferably obtained as a wound body in which the longitudinal direction (MD) of the inflation biaxial stretching is the winding direction. Thereby, the length direction of the wrap film is the same as the longitudinal direction (MD) of the inflation biaxial stretching, and the cutting can be easily performed with a small force.

[Examples]

Hereinafter, the present invention will be more specifically described based on examples and comparative examples, but the present invention is not limited to the following examples. Further, the specific viscosity of the polyvinylidene chloride-based resin, the birefringence difference of the wrap film, and the degree of plane orientation were measured by the following methods.

(1) Concentrated viscosity

1 g of a polyvinylidene chloride-based resin was added to 50 ml of tetrahydrofuran, and the mixture was heated to 40 ° C to be dissolved. This solution was added to methanol to deposit a polyvinylidene chloride-based resin, which was recovered by filtration and dried. 80 mg of the polyvinylidene chloride-based resin after drying was weighed, and 20 ml of cyclohexanone at 30 ° C was added as a solvent, and the mixture was heated at 70 ° C for 60 minutes to be dissolved. Thereafter, it was cooled at room temperature and filtered to obtain a sample solution.

5 ml of the sample solution was injected into an Ubbelohde viscometer, and after standing for 5 minutes in a thermostat at 30 ° C, the number of seconds of the sample solution was measured by a conventional method, by the following formula: η = (1/4 ×{(t ₂ /t ₁ )-1} (wherein t ₁ represents the number of seconds of flow of cyclohexanone (solvent) at 30 ° C (unit: second), and t ₂ represents a flow of the sample solution at 30 ° C The number of seconds (in seconds) is calculated as the viscosity (η).

(2) Double refractive index difference

The wrap film was attached to a phase difference measuring device ("KOBRA-WR" manufactured by Oji Scientific Instruments Co., Ltd.) in the direction of the film (MD) in the 0° direction of the measuring device, and the in-plane retardation of the wrap film at a wavelength of 589 nm was measured. The amount Re is represented by the following formula (1): Δn = n _{x -} n _y = Re / d (1) (wherein n _x represents the refractive index in the slow axis direction of the film, and n _y represents the in-plane of the film Refractive index perpendicular to the direction of the slow axis direction, Re represents the in-plane hysteresis amount of the film (unit: nm), and d represents the film thickness (unit: nm))

The birefringence difference Δn of the wrap film was calculated. The measurement was carried out for 5 randomly selected measurement points, and the average value was calculated. In addition, the fifth digit after the decimal point is rounded off, and the value of four digits after the decimal point is taken as the average value. Further, the orientation angle is displayed in the range of -90 to 90 degrees. Thereby, if the orientation angle is in the range of -45 to 45 degrees, the polyvinylidene chloride has a negative intrinsic birefringence, which means that the slow axis direction of the wrap film is the longitudinal direction (MD). That is, it means that the transverse (TD) orientation of the wrap film is stronger than the longitudinal direction (MD), and as Δn becomes smaller, the orientation of the longitudinal direction (MD) becomes stronger.

(3) Plane orientation

The wrap film was attached to a phase difference measuring device ("KOBRA-WR" manufactured by Oji Scientific Instruments Co., Ltd.) so that the film was oriented so that the tilting center axis was fast. The axis, the incident angle is 40°, and the average refractive index Nave=1.609, the refractive index n _x in the in-plane slow axis direction of the wrap film at a wavelength of 589 nm in the low phase difference mode, and the in-plane perpendicular to the slow axis direction The refractive index n _y in the direction and the refractive index n _{z in the} thickness direction are calculated by the following formula (2): ΔP = (n _x + n _y )/2 - n _z (2) Degree △ P. The measurement was carried out for 5 randomly selected measurement points, and the average value was calculated. In addition, the fifth digit after the decimal point is rounded off, and the value of four digits after the decimal point is taken as the average value.

(Preparation Example 1)

VD:VC=82:18 (mass ratio) mixed with vinylidene chloride (VD) and vinyl chloride (VC), synthesizing vinylidene chloride-vinyl chloride copolymer by suspension polymerization (PVDC resin, specific viscosity ( η): 0.044 L/g). To 100 parts by mass of the PVDC resin, 8.4 parts by mass of butyl tributyl citrate (ATBC), diethylated monoglyceride (DALG), epoxidized soybean oil and liquid paraffin were added as an additive and mixed. PVDC resin composition.

(Example 1)

A wrap film was produced using the manufacturing apparatus shown in FIG. That is, using a uniaxial extruder 1 having a diameter of 75 cm, the PVDC resin composition obtained in Formulation Example 1 was melted from a circular mold at 175 ° C, and then a cooling bath of 10 ° C was used. (First Bath) 2 The obtained tubular parison was quenched, and then passed through a warm water bath (second bath) 3 at 40 °C. Thereafter, between the rolls 4 and 5 having different rotation speeds, the tubular parison is forced into air to be expanded, and the inflation double is performed at an extension ratio of an extension temperature of 25° C., a longitudinal direction (MD) of 4.2 times, and a lateral direction (TD) of 5.1 times. The shaft is extended, and further, between the rolls 5 and 6 having different rotation speeds, the relaxation treatment is performed at a relaxation rate of 25 ° C, a longitudinal direction (MD) of 10.1%, and a transverse direction (TD) of 4.0%, and then the winding roller 7 is used. Then, longitudinal cutting and rewinding were carried out to obtain a wrap film wound body (width: 30 cm) having a roll length of 20 m. Further, the extension temperature is a temperature of a gaseous environment (ie, an ambient temperature in a region between the rolls 4 and 5) exposed when the tubular parison taken out from the second bath is biaxially stretched, and the relaxation temperature is biaxial. The temperature of the gaseous environment (i.e., the ambient temperature in the region between the rolls 5 and 6) when the film is subjected to relaxation treatment after stretching. The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

(Example 2)

The pneumatic biaxial stretching was carried out at a stretching ratio of an extension temperature of 25 ° C, a longitudinal direction (MD) of 4.4 times, and a transverse direction (TD) of 5.0 times, and a relaxation temperature of 25 ° C, a longitudinal direction (MD) of 10.1%, and a transverse direction (TD) of 4.8%. The wrap film was wound in the same manner as in Example 1 except that the relaxation rate was subjected to the relaxation treatment. The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. In addition, the obtained The orientation angle of the cling film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

(Example 3)

The pneumatic biaxial stretching was carried out at a stretching ratio of an extension temperature of 25 ° C, a longitudinal direction (MD) of 4.6 times, and a transverse direction (TD) of 4.7 times, and a relaxation temperature of 25 ° C, a longitudinal direction (MD) of 5.0%, and a transverse direction (TD) of 5.1%. The wrap film was wound in the same manner as in Example 1 except that the relaxation rate was subjected to the relaxation treatment. The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

(Example 4)

In addition to changing the temperature of the cooling bath (first bath) to 11 ° C, the temperature of the warm water bath (second bath) was changed to 45 ° C, and the elongation temperature was 25 ° C, the machine direction (MD) was 4.0 times, and the lateral direction (TD) was 5.1 times. The stretching ratio was subjected to a pneumatic biaxial stretching, and the relaxation treatment was carried out at a relaxation temperature of 25 ° C, a longitudinal direction (MD) of 5.0%, and a transverse direction (TD) of 5.3%. The other operations were the same as in Example 1, and a wrap film was prepared. Winding around. The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. This shows that The slow axis direction of the obtained wrap film is the machine direction (MD), and the transverse direction (TD) direction is stronger than the machine direction (MD).

(Example 5)

The pneumatic biaxial stretching was carried out at a stretching ratio of an elongation temperature of 25 ° C, a longitudinal direction (MD) of 4.5 times, and a transverse direction (TD) of 4.8 times, and a relaxation temperature of 25 ° C, a longitudinal direction (MD) of 5.0%, and a transverse direction (TD) of 4.0%. A wrap film wound body was produced in the same manner as in Example 4 except that the relaxation rate was subjected to the relaxation treatment. The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

(Example 6)

In addition to changing the temperature of the warm water bath (second bath) to 30 ° C, the inflation biaxial stretching was carried out at an extension ratio of elongation temperature 30 ° C, longitudinal direction (MD) 4.2 times, and lateral direction (TD) 4.6 times, and the relaxation temperature was 40 ° C. The wrap film was prepared in the same manner as in Example 4 except that the relaxation ratio was 10.8% in the machine direction (MD) and 4.2% in the transverse direction (TD). The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

(Example 7)

The pneumatic biaxial stretching was carried out at an extension ratio of an elongation temperature of 30 ° C, a longitudinal direction (MD) of 4.1 times, and a transverse direction (TD) of 4.8 times, and a relaxation temperature of 40 ° C, a longitudinal direction (MD) of 10.7%, and a transverse direction (TD) of 6.1%. The wrap film was wound in the same manner as in Example 6 except that the relaxation rate was subjected to the relaxation treatment. The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

(Example 8)

The pneumatic biaxial stretching was carried out at a stretching ratio of an extension temperature of 30 ° C, a longitudinal direction (MD) of 4.3 times, and a transverse direction (TD) of 4.5 times, and a relaxation temperature of 40 ° C, a longitudinal direction (MD) of 10.7%, and a transverse direction (TD) of 4.3%. The wrap film was wound in the same manner as in Example 6 except that the relaxation rate was subjected to the relaxation treatment. The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

(Comparative Example 1)

The pneumatic biaxial stretching was carried out at a stretching ratio of an extension temperature of 25 ° C, a longitudinal direction (MD) of 3.2 times, and a transverse direction (TD) of 5.4 times, and a relaxation temperature of 25 ° C, a longitudinal direction (MD) of 10.1%, and a transverse direction (TD) of 4.9%. The wrap film was wound in the same manner as in Example 1 except that the relaxation rate was subjected to the relaxation treatment. The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

(Comparative Example 2)

The pneumatic biaxial stretching was carried out at an extension ratio of an extension temperature of 25 ° C, a longitudinal direction (MD) of 3.4 times, and a lateral direction (TD) of 3.3 times, and a relaxation temperature of 25 ° C, a longitudinal direction (MD) of 10.1%, and a transverse direction (TD) of 3.5%. The wrap film was wound in the same manner as in Example 1 except that the relaxation rate was subjected to the relaxation treatment. The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

(Comparative Example 3)

The pneumatic biaxial stretching was carried out at an extension ratio of 25 ° C, 3.4 times in the machine direction (MD), and 4.4 times in the transverse direction (TD), and the relaxation temperature was 25 ° C, and the longitudinal direction was A wrap film wound body was produced in the same manner as in Example 1 except that the relaxation ratio of (MD) 10.1% and the transverse direction (TD) of 3.5% was carried out. The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

(Comparative Example 4)

In addition to changing the temperature of the cooling bath (first bath) to 12 ° C, the temperature of the warm water bath (second bath) was changed to 30 ° C, the elongation temperature was 25 ° C, the machine direction (MD) was 4.0 times, and the lateral direction (TD) was 5.1 times. The stretching ratio was subjected to a pneumatic biaxial stretching, and the relaxation treatment was carried out at a relaxation temperature of 25 ° C, a longitudinal direction (MD) of 10.1%, and a transverse direction (TD) of 3.9%. The other operations were the same as in Example 1, and a wrap film was prepared. Winding around. The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

(Comparative Example 5)

The pneumatic biaxial stretching was carried out at a stretching ratio of extension temperature of 25 ° C, longitudinal direction (MD) of 3.5 times, and lateral direction (TD) of 5.3 times, and the relaxation temperature was 25 ° C, the longitudinal direction (MD) was 5.0%, and the transverse direction (TD) was 5.2%. Relaxation rate other than relaxation treatment, other The operation was carried out in the same manner as in Example 4, and a wrap film wound body was produced. The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

(Comparative Example 6)

The pneumatic biaxial stretching was carried out at a stretching ratio of extension temperature of 25 ° C, longitudinal direction (MD) of 4.0 times, and transverse direction (TD) of 4.7 times, and the relaxation temperature was 25 ° C, the longitudinal direction (MD) was 5.0%, and the transverse direction (TD) was 5.8%. A wrap film wound body was produced in the same manner as in Example 4 except that the relaxation rate was subjected to the relaxation treatment. The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

(Comparative Example 7)

The pneumatic biaxial stretching was carried out at a stretching ratio of extension temperature of 30 ° C, longitudinal direction (MD) of 4.0 times, and transverse direction (TD) of 4.7 times, and the relaxation temperature was 40 ° C, the longitudinal direction (MD) was 10.8%, and the transverse direction (TD) was 4.2%. The wrap film was wound in the same manner as in Example 6 except that the relaxation rate was subjected to the relaxation treatment. Calculate the thickness of the cling film obtained, calculate the birefringence difference Δn (average value) and plane take The degree of orientation ΔP (average value). The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

(Comparative Example 8)

The pneumatic biaxial stretching was carried out at a stretching ratio of extension temperature of 30 ° C, longitudinal direction (MD) of 4.0 times, and transverse direction (TD) of 4.7 times, and the relaxation temperature was 40 ° C, the longitudinal direction (MD) was 10.7%, and the transverse direction (TD) was 4.6%. The wrap film was wound in the same manner as in Example 6 except that the relaxation rate was subjected to the relaxation treatment. The thickness of the obtained cling film was measured, and the birefringence difference Δn (average value) and the plane orientation degree ΔP (average value) were calculated. The results are shown in Table 1. Further, the orientation angle of the obtained wrap film is in the range of -45 to 45 degrees. From this, it is understood that the obtained slow direction of the wrap film is in the machine direction (MD), and the cross direction (TD) direction is stronger than the machine direction (MD).

<Cutting (Functional Test)>

The wrap film wound body obtained in the examples and the comparative examples was placed in a commercially available NEW Krewrap (registered trademark) paper cassette (for 30 cm width) on which resin serrated teeth were attached. Pull out the plastic wrap from the paper tray for about 30cm, then firmly close the carton cover, hold the carton and position the thumb at the specified position, turn the carton inward, and cut the plastic wrap from the center toward the lateral (TD) side. . The cutting of the wrap film was carried out for 10 supervisors, and the judgment was made based on the following criteria. The results are shown in Table 1.

A: It is easy to cut with less force.

B: It can be cut with less force, but it is difficult to cut.

C: It cannot be cut with less force and requires a lot of force.

<Cutting (cropping test)>

The wrap film obtained in the examples and the comparative examples was cut into a transverse direction (TD) of 40 mm and a machine direction (MD) of 140 mm to prepare a wrap film for testing. In the inside of a NEW Krewrap (registered trademark) paper box (for 30 cm wide), which is a commercially available new product made of resin serrated, the longitudinal (MD) end of the test wrap is fixed with a tape and attached to a special jig. At that time, the center portion of the test wrap film exposed from the paper cassette is fixed in contact with the tip end of the V-shaped portion of the carousel. Then, the other end of the longitudinal direction (MD) of the test wrap film was held by the chuck portion of the TENSILON Universal Material Testing Machine ("RTC-210A" manufactured by Orientec Co., Ltd.), and the angle of the jig was adjusted to make the sawtooth and the test wrap. The angle is 80°. Then, the test wrap film was stretched upward at a tensile speed of 1000 mm/min, and the strength (peak (unit: N)) when the wrap film was cut was measured, and the wrap film obtained in Example 1 was cut. The force was divided by the cutting force of the wrap film obtained in each Example, and the relative number of points was calculated based on the cutting force of the wrap film obtained in Example 1. The results are shown in Table 1. In addition, if the relative number of the cling film is 1.00 or more, it means that the wrap film is easy to cut, and it is only required to have the same force as the wrap film obtained in the first embodiment; on the other hand, if the cling film is When the relative number of dots is less than 1.00, it indicates that the wrap film is difficult to be cut, and it is necessary to use a force larger than that of the wrap film obtained in Example 1.

Comparing the plane orientation degree ΔP of Example 7 and Comparative Example 4 shown in Table 1 with the birefringence difference Δn, it was found that ΔP was the same, but Δn of Example 7 was small, indicating the longitudinal direction ( MD) has a larger molecular orientation. Regarding the cutting property of the wrap film of the present invention, the degree of breakage when the film is stretched in the vertical direction of the serration is evaluated, so that it is presumed that the stretching direction (longitudinal direction of the wrap film) and the longitudinal direction of the inflated biaxially When (MD) is uniform, the wrap film described in Example 7 in which the molecular orientation of the machine direction (MD) is large is easily broken. On the other hand, Δn of Comparative Example 6 was smaller than that of Example 7, but ΔP was larger than that of Example 7, and it was difficult to break.

Based on the results shown in Table 1, the plane orientation degree ΔP is plotted with respect to the birefringence difference Δn. The result is shown in Figure 2.

As is clear from the results shown in Table 1 and FIG. 2, the birefringence difference Δn satisfies the following formula (1a): The condition and plane orientation degree ΔP expressed by the following formula (2a) are satisfied: The wrap film (Examples 1 to 8 and the dotted line frame of Fig. 2) of the indicated conditions can be easily cut by a small force, and the wrap film obtained in Examples 2 to 8 is obtained in comparison with Example 1. The relative number of dots of the wrap film is 1.00 or more.

On the other hand, the wrap film (Comparative Examples 1, 4 to 5) in which the birefringence difference Δn does not satisfy the condition expressed by the formula (1a) and the plane orientation degree ΔP do not satisfy the expression (2a) The cling film (Comparative Examples 1 to 3, 5 to 8) was difficult to cut with a small force, or could not be cut with a small force, as opposed to the relative thickness of the wrap film obtained in Example 1. Lower than the number of points 1.00. In particular, the wrap film (Comparative Examples 1 to 3) having a plane orientation degree ΔP of -0.0093 or more cannot be cut with a small force, and requires a large force, relative to the wrap film obtained in Example 1. The number of points is below 0.68.

[Industrial Availability]

As described above, according to the present invention, a PVDC resin wrap film which can be easily cut with a small force can be obtained.

Therefore, the wrap film of the present invention is less likely to be torn in the longitudinal direction and can suppress the deterioration of the carton serration, and therefore can be used as a wrap film for various packagings such as household wrap films.

Claims (8)

A wrap film comprising a wrap film of a polyvinylidene chloride-based resin, wherein, by the following formula (1): Δn=n _x -n _y =Re/d (1), n _x represents The refractive index of the slow axis direction of the film in the plane, n _y represents the refractive index in the direction perpendicular to the slow axis direction of the film, Re represents the in-plane hysteresis of the film (unit: nm), and d represents the film thickness (unit: nm) ), the calculated birefringence difference Δn satisfies the following formula (1a): The condition expressed by the following formula (2): ΔP = (n _x + n _y ) / 2 - n _z (2) where n _x represents the refractive index of the in-plane slow axis direction of the film, n _y A refractive index indicating a direction perpendicular to the slow axis direction in the plane of the film, n _z represents a refractive index in the thickness direction of the film, and the calculated plane orientation degree ΔP satisfies the following formula (2a): The conditions indicated. The wrap film of claim 1, wherein the wrap film has a thickness of 5 to 15 μm. The wrap film according to claim 1, wherein the polyvinylidene chloride-based resin is a copolymer of vinylidene chloride and a comonomer copolymerizable with the vinylidene chloride. The wrap film according to claim 2, wherein the polyvinylidene chloride-based resin is a copolymer of vinylidene chloride and a comonomer copolymerizable with the vinylidene chloride. The wrap film of claim 3, wherein the comonomer is vinyl chloride. The wrap film of claim 4, wherein the comonomer is vinyl chloride. The wrap film according to any one of claims 1 to 6, wherein the in-plane slow axis direction is a longitudinal direction (MD) of the wrap film. A wrap film wound body comprising a wrap film according to claim 7 of the patent application, wherein the wrap film has a machine direction (MD) in a winding direction and is loaded into a carton in which a serration is attached.